Cephalometric imaging (or transillumination imaging) is regularly used by dental practitioners, for example, in orthodontic applications. For cephalometric imaging techniques, an image of the x-ray radiated skull of the patient is projected on an x-ray sensitive surface located away from the x-ray source using a cephalometric arm. In most of the cases, the sensor is positioned at the extremity of a long cephalometric arm and is positioned at a distance about 1.7 meters away from the x-ray source. The necessity to have the sensor positioned far away from the x-ray source originates from the necessity to have an approximately equal magnitude factor for every part of the patient's skull. The imaging process may consist in one single shot of the patient's skull with the x-ray beam impinging a full (e.g., square) sensor after radiating the patient. As an alternative to decrease the size of the sensor, a linear elongated sensor can be used in association with a linearly elongated (e.g., vertical) slit-shaped collimator that aims at shaping the x-ray beam before the x-ray beam radiates the patient. The patient is positioned between the elongated collimator and the elongated sensor. A linear scan can be performed by horizontally translating a vertically elongated sensor and a vertically elongated collimator and changing the direction of the x-ray beam accordingly through the use of a primary collimator positioned in front of the X-ray source. The images collected during the scan are merged together to form a projection of the patient's skull. In the cephalometric or skull imaging technique, the patient can be positioned facing the x-ray beam or in a profile position.
In order to obtain a skull profile image of the best quality, the sagittal plane of the skull must be parallel to the plane of the sensor at the time of the imaging and orthogonal to the median line of the x-ray beam. Consequently, when a cephalometric imaging apparatus is first installed in a dental site by a technician, it is necessary to adjust the position of the whole cephalometric imaging module, comprising the x-ray sensor and a patient holder, relative to the x-ray source, prior to any cephalometric imaging of patients. According to the prior art, at least two radiopaque markers are located on the patient holder and a first x-ray control image of the patient holder (without any patient) is carried out. If the images of the at least two markers superimpose on the x-ray image, the cephalometric module is conveniently or correctly positioned relative to the x-ray source. On the contrary, if the images of the two markers do not superimpose, the cephalometric module is misaligned relative to the x-ray source and needs to be repositioned before capturing a second control image or additional control images.
One drawback of the prior art process is because the technician who installs the cephalometric imaging device does not know, at the time he changes the adjustment of the cephalometric module, whether the new adjustment is correct. Only subsequent control images taken after adjustment will give an assessment of the quality of the adjustment. Accordingly, the cephalometric installation requires an adjustment process including a repeated, back and forth method of (i) successive adjustments of the cephalometric module to the x-ray source and (ii) successive assessments by taking a follow-up control image. This repetitious installation process is highly cumbersome, time consuming, and/or increases the cost of the installation of the cephalometric imaging device by the technician.
It can be appreciated that there is still a need for installation apparatus and/or methods that can provide a cheaper, rapid, accurate and/or real time assessment of a correctness of an installation/adjustment of a cephalometric module and/or dental cephalometric imaging device.